The lack of communicative interaction skills contributes to the academic as well as the social skill deficits demonstrated by developmentally disabled children. This communication skill deficiency interferes with the acceptance and the successful integration of developmentally disabled children into mainstream settings. This proposed research will investigate variables suspected to influence the development of effective communicative interaction skills in developmentally disabled and normally developing preschoolers. The goals of this proposed research include: (1) describing the natural communicative interaction among handicapped and nonhandicapped children; (2) evaluating a peer-mediated intervention program based on the identification of naturally occurring strategies that facilitate interaction; (3) investigating methods to increase generalization and maintenance of peers' use of facilitative strategies and decrease the amount of direct teacher involvement; and (4) investigating the efficacy of teaching strategies to developmentally disabled children that facilitate longer conversational interchanges. The long-term objective of this research is to develop a communicative interaction intervention program that will maximize the use of language by severely developmentally disabled children and secondarily to enrich their potential to learn cognitive and social skills through language. The proposed research will be conducted in four integrated preschool classrooms that serve normally developing children and children with handicapping conditions that include developmental disabilities, behavior disorders, and language delays. During the proposed funding period at least 56 normally developing children and 16 developmentally disabled children will participate in the proposed studies. The proposed plan of research involves six studies; two are descriptive studies and four use single-subject experimental designs. The planned research has implications for the development of an ecobehavioral model of communicative development and is most significant in its direct contribution to the development of more effective procedures that can be employed during a critical period of early development in developmentally disabled children.